Difference between Static methods and Instance methods

The basic paradigm in Java is that you write classes, and that those classes are instantiated. Instantiated objects (an instance of a class) have attributes associated with them (member variables) that affect their behavior; when the instance has its method executed it will refer to these variables.

However, all objects of a particular type might have behavior that is not dependent at all on member variables; these methods are best made static. By being static, no instance of the class is required to run the method.

You can do this to execute a static method:

MyClass.staticMethod();  // Simply refers to the class's static code

But to execute a non-static method, you must do this:

MyClass obj = new MyClass();//Create an instanceobj.nonstaticMethod();  // Refer to the instance's class's code

On a deeper level the compiler, when it puts a class together, collects pointers to methods and attaches them to the class. When those methods are executed it follows the pointers and executes the code at the far end. If a class is instantiated, the created object contains a pointer to the "virtual method table", which points to the methods to be called for that particular class in the inheritance hierarchy. However, if the method is static, no "virtual method table" is needed: all calls to that method go to the exact same place in memory to execute the exact same code. For that reason, in high-performance systems it's better to use a static method if you are not reliant on instance variables.

Methods and variables that are not declared as static are known as instance methods and instance variables. To refer to instance methods and variables, you must instantiate the class first means you should create an object of that class first.For static you don't need to instantiate the class u can access the methods and variables with the class name using period sign which is in (.)

for example:

Person.staticMethod();           //accessing static method.

for non-static method you must instantiate the class.

Person person1 = new Person();   //instantiatingperson1.nonStaticMethod();       //accessing non-static method.

Difference between Static methods and Instance methods

1. Instance method are methods which require an object of its class to be created before it can be called. Static methods are the methods in Java that can be called without creating an object of class.

2. Static method is declared with static keyword. Instance method is not with static keyword.

3. Static method means which will exist as a single copy for a class. But instance methods exist as multiple copies depending on the number of instances created for that class.

4. Static methods can be invoked by using class reference. Instance or non static methods are invoked by using object reference.

5. Static methods can’t access instance methods and instance variables directly. Instance method can access static variables and static methods directly.

Reference : geeksforgeeks